This invention relates to optoelectronic switching apparatus and in particular an optoelectronic switching matrix which can be used to form a variety of signal processing elements.
Broadband signal processing, particularly of signals having frequencies higher than 100 MHz requires the use of elements or components which have not, to a large extent, yet been satisfactorily realized. The present invention is an apparatus which, in different embodiments, can provide programmable signal delay, programmable bandpass filtering, digital parallel to serial conversion at high data rate, digital matched filtering, and programmable high rate digital word generation, for example. The invention depends on the provision of an optoelectronic switching matrix, which has high isolation between optical waveguide signal paths, wideband and signal summation, and unidirectional cross points.
In the past, bandpass filters have been constructed from tapped delay lines, but the length of the delay lines has been difficult to vary dynamically. Techniques for achieving varying delays with lengths of transmission line to cover a broad frequency range have been difficult to utilize. Consequently in the past, easily realizable circuit elements have not become available for use with wideband signals in excess of 100 MHz.
Such circuit elements are readily and easily achievable in the invention described below. One of the important elements of the inventive combination is an optoelectronic switching matrix. The characteristics of the elements can be easily varied by the programmed operation of the switching matrix.